Automobile deceleration signal switching circuit



March 5, 1968 w, CARPENTER ET AL 3,372,372

AUTOMOBILE DECELERATION SIGNAL SWITCHING CIRCUIT Filed March 31, 1965 ZZZ%M ATTORNEYS United States Patent OfiFice 3,372,372 AUTOMOBILE DECELERATION SIGNAL SWITCHING CIRCUIT William R. Carpenter, Muskegon, and David G. Passmore, Cornstock Park, Mich, assignors, by mesne assignments, to Medallion Instruments, Ine., Spring Lake, Mich, a corporation of Michigan Filed Mar. 31, 1965, Ser. No. 444,266 7 Claims. (Cl. 340-71) ABSTRACT OF THE DISCLOSURE A circuit for switching on an incandescent alarm lamp in response to deceleration of a motor vehicle, in which a relatively high-impedance branch of the circuit constantly maintains a very low current through the lamp sufficient only to warm its filaments lbut insuflicient to drive the same into incandescence, and wherein a switch means senses the engine vacuum and upon deceleration conditions closes a shorting circuit across the aforesaid high impedance branch to raise the current flow through the indicating lamp and cause incandescence thereof. The vacuum-sensing switch means incorporates a diaphragmoperated contact, a relatively fixed contact, and a floating contact positioned therebetween which is attached to neither and which can move between them to keep such contacts clean and unpitted.

This invention relates to motor vehicle safety signalling devices, and more particularly to a new and unique warning or alarm system for instantly indicating that a vehicle has begun to decelerate, long before the stop lights of the vehicle may be actuated and without regard to whether or not the stop lights or other such signals actually operate.

The advent of a national system of turnpikes and throughways and the emergence of multiple crosstown parkways in many of the larger cities in the country have created the requirement for a vehicle in a series begins to decelerate, the probability of a rear-end collision increases tremendously, and indeed this type of accident is by far the most frequent on such highways.

The high probability of accident under these circumstances is due in the first instance to the fact that the allowable reaction time rapidly enough to avoid an accident. Further-more, when a second, third, or subsequent driver must depend for his danger signal upon the reaction of the drivers between 3,372,372 Patented Mar. 5, 1968 himself and the leader, the reason becomes clear why a progression of succeeding rear-end collisions becomes practically unavoidable once the lead driver has initiated the same by the original deceleration.

While it is true that the customary stop lights of vehicles serve to give a certain degree of warning, such lights operate only when the brake pedal is pushed downward. Consequently, the stop lights do not operate at all to subsequent drivers, to the extent that at some point vehicles it will literally become impossible to decelerate sufiiciently to avoid collision in the remaining shortened reaction time available. Vital seconds are lost between the time the first driver removes his foot from the accelerator and the time he places his foot avoid the impending collision entirely.

It has been suggested in the past to provide a warning signal at the rear of vehicles which would provide a clear indication that the vehicle was decelerating,

properly, they are extremely expensive and the units which utilize them are accordingly rendered unattractive and competitively unfeasible.

It is an important objective of the present invention to provide an alarm system for instantly and unfailingly signalling a predetermined degree of deceleration in motor vehicles, as the circumstances detailed above clearly show to be imperative.

Another objective of the present invention is to provide an alarm system of the nature described which senses the operate.

clearly upon a complete consideration of the following In the drawings:

FIG. 1 is a schematic representation of the preferred circuit for energizing the alarm; and

FIG. 2 is a central sectional side elevation view of the vacuum-sensing switch mechanism.

Stated briefly, the present invention provides an alarm system for motor vehicles comprising basically a vivid and eye-catching indicating means such as a bright amber or other colored light, and a circuit for energizing this indicator when the vehicle is in a condition of deceleration, in order to instantly convey knowledge to those behind the vehicle that it is so decelerating. The energizing circuit includes a novel auxiliary branch which maintains the indicating device in a ready condition by completing a circuit through it in which a very small current fiows at all times, even though the indicator itself is not actuated. This greatly extends the life of the indicator and greatly facilitates its actuation. The indicator is actuated by a unique vacuum-sensing switch means which monitors the partial or negative pressures present in the intake manifold of the vehicle when its engine is running, and immediately energizes the indicator upon the occurrence of any perceptible deceleration of the engine causing the vehicle to slow.

Referring now in greater detail to the drawings, the circuit of FIG. 1 includes a source of energizing power 10, which is preferably the battery of the motor vehicle, and an indicating element 12, which is preferably an incandescent light having a desired degree of brilliance to instantly attract attention when illuminated. The source and the light 12 are preferably connected in series, and a path is completed to the circuit ground through a resistor 14. It is important that the latter element have a resistance value so large that although a current does flow through the lamp 12,- it is very small in magnitude and only causes the filaments in the lamp to remain in a warm condition. In this state the excitation of the lamp is well below its incandescent value, and consequently the lamp may be said to be not actuated, since to all appearances it is dark and gives no signal.

Connected in shunt directly across resistor 14 is an alternative circuit branch 16. Branch 16 includes only a switching means 18, which is normally open. Consequently, this branch is normally inactive, and the circuit operates in the aforesaid manner. However, when switching means 18 is actuated to close its contacts, it will be seen that a direct short is placed across resistor 14 and it consequently is in effect removed from the circuit. This results in a very large current flow through the lamp 12, causing it to become incandescent and giving the desired alarm signal.

The switching means 18 of FIG. 1 is a vacuum-sensing device which operates to close its contacts upon sensing a predetermined level of vacuum. Switching means 1% is shown in great detail in FIG. 2.

The switching means 18 of FIG. 2 includes basically an enclosing two-piece housing comprised of a switch housing 20 at the lower end and a cavity-enclosing cover 22 at the top. The switch housing 2%} is made of a suitable metal and is electrically conductive, whereas the cover 22 is not electrically conductive and is preferably formed from a suitable plastic or the like. It is to be noted that the lowermost end of the switch housing 29 converges into a generally cylindrical mounting portion 24 having external threads formed thereupon. Further, the opposite extremity of the switch housing flares outwardly into a bell housing 26 which may have interior threads 28 formed therein. The switch housing 20 and cover 22 are secured together as by threading the latter into the bell housing threads 23 of the former.

It will be noted that the assembled switch housing and cover form an enclosure, and that this enclosure houses a number of components. A clinch nut 36 grips the sides of an opening formed in the top of the cover 22 generally centrally thereof. The clinch nut secures a male spade connector 32 to the cover, and also provides a threaded aperture for receiving an adjustment screw 34. The inner end of the adjustment screw 34 bears downwardly agamst the end plate 36 of a pressure-regulating spring 38. The other end of this spring bears against a washer-like disk 40, which forms one of the switching contacts of the device.

Immediately beneath the disk contact 40 is a second similar member 4-2 which in effect floats between contact 40 and an annular contact sleeve 44. The outer periphery of the contact sleeve 44 is relieved to form an outwardlyprojecting shoulder 46, which abuts a matching projection on the interior of the cover 22. The abutment of the shoulder 46 of contact sleeve 44 against the interior of the cover acts to positively prevent the contact sleeve from moving upward relative to the cover, and a ring plate 48 upon which the contact sleeve rests secures the latter immovably in place between the cover and the ring plate, preventing any downward movement of the latter. The ring plate 48 is itself secured in position by virtue of a direct abutting contact with the end extremities of the cover 22, as shown. The ring plate 48 is a substantially rigid disk with an aperture at its center, and like all of the elements within the cover thus far identified, is to be formed from an electrically-conductive material.

It will be noted that a plunger 50 is positioned concentrically of and within the contact sleeve 44. Plunger 50 is formed from an insulating material and fits freely in place, being readily movable relative to the contact sleeve. The top of plunger 50 bears against the under-surface of the floating contact washer 42, Whereas the bottom of the plunger bears directly against and rides upon the surface of a flexible pressure-sensitive diaphragm 52, which is firmly secured about its outer periphery by being clamped in .place between an inner shoulder of the bell housing an of switch housing .20 and the ring plate 48 and cover 22 when the cover and switch housing are securely tightened against each other. Thus, the diaphragm 52 is prevented by the ring plate from moving upward beyond a horizontal position, but is not prevented from moving downwardly away from this position. Like the plunger 50, the diaphragm 52 is made fro-m an insulating material.

An upwardly-directed force is exerted against the underside of the diaphragtm 52 by a biasing spring '54 seated in an appropriate relieved portion in the interior of the switch housing 20. .Biasing spring 54 has a cap structure 56 hooding its upper extremity for contacting the surface of the diaphragm and distributing the force of the spring 54 over the central portion of the diaphragm. To complete the description of the switch means 18, it will be observed that a rivet 58 is placed concentrically through the contact 40, the floating contact 42, and the plunger 50, and headed at 60. The shank of the rive-t 58 is of sufiicient length to allow the contacts to be spaced one from the other under certain conditions, yet limits the total distance by which they may be separated. The shank of the rivet serves to maintain the two contacts and the plunger in the desired concentric alignment.

In operation, the switch means 18 is threaded into an appropriate tapped aperture (not shown) formed in the intake manifold of the internal combustion engine of a motor vehicle by means of its threaded mounting projection 24. The signal lamp 12 of FIG. 1 is connected in the manner there shown and positioned in the rear window of the vehicle, or other prominent easily-observed position. The warming resistor 14 is connected as shown, and the lead connecting switch means 18 into the auxiliary branch 16 is connected to the spade connection 32 at the top of the switch means cover 22. Under these circumstances, the trickle of warming current described previously is conducted through the filaments of the lamp 12, but it is as yet unlighted and gives no warning signal.

As is well known, a running internal combustion engine produces a vacuum in its intake manifold, which varies in accordance with several dilferent factors. Foremost among these factors is the amount of loading placed upon the engine. Thus, an engine which is being accelerated or which is laboring has a very low vacuum in its intake manifold (perhaps as low as from one to one and onehalf inches Hg), an engine being run steadily at an even pace with only moderate loading will produce a higher intake manifold vacuum-(perhaps ten to fifteen inches Hg), and an idling, unloaded engine will develop a very high vacuum (as much as twenty inches Hg). The maximum intake manifold pressure (i.e., vacuum) is produced during deceleration, however, and this may easily reach as much as twenty-five inches Hg or even higher, depending again upon the size of the load and the compressive braking action of the engine against that load.

Accordingly, an average engine in a motor vehicle being driven at parkway and turnpike speeds will develop a manifold pressure in the medium range, of perhaps ten to fifteen inches Hg, whereas if the same engine is decelerated even a relatively slight amount by merely backing off the throttle slightly, its manifold pressure will rapidly jump from the previous level to a high level of approximately twenty-five inches or more. Furthermore, the high manifold pressure will continue as long as the engine is decelerating.

This characteristic of internal combustion engines is utilized by the present invention to close the normally open contacts in switching means 18. When this is done and circuit branch 16 (FIG. 1) is closed, resistor 14 is shorted out and a much higher current flow is produced through the lamp 12 to actuate it and cause it to be illuminated, thereby giving a warning signal to those vehicles following the one which is decelerating, that such condition is in existence and that they must take care. Such warning signal is of course completely unconnected to any braking of the vehicle, and will occur whether or not the brakes are applied, even though the deceleration is relatively slight. Further, even though the brakes may subsequently be applied, the critical reaction time of the average driver between the moment of his mental recognition of the need to slow down, when he almost involuntarily releases the accelerator somewhat, and the moment when he has actually moved his foot from accelerator to brake to apply the latter is eliminated and does not occur. Instead, the warning signal of the present invention will immediately flash at the rear of the decelerating vehicle to warn others following.

The switching of the contacts by the switch means 13 occurs as a result of the high vacuum present in the intake manifold during deceleration. With the mounting p-onti-on 24 of the switch means threaded into the intake manifold, the pressure in the manifold acts through passageway 62 in the switch housing 20 and against the underside of the diaphragm 52. Spring 38 in the upper por tion of the switch and spring 54 in the lower portion exert oppositely-directed forces which act on each side of the diaphragm. Further, atmospheric pressure which is trapped in the various recesses of the cover 22 acts downwardly against the diaphragm. Consequently, the diaphragm is balanced between the downwardly-directed forces of atmospheric pressure plus pressure from spring 38, and the upwardly-directed forces due to spring 54 plus, of course, the Varying amounts of vacuum from the intake manifold. Accordingly, the diaphragm will be in its uppermost position immediately adjacent ring plate 48 when the engine produces the least amount of vacuum, and it will be deformed downwardly in a direct relation to increased amounts of vacuum produced by the engine.

When the vehicle is being accelerated or driven at a constant and steady rate, voltage connected to the switch means 18 at connection 32 will be connected through the clinch nut 30 and adjusting screw 34, through end plate 36, spring 33, and contact washer 40. Because the diaphragm 52 senses only small to moderate amounts of vacuum under these conditions, it occupies an upward position, close to ring plate 48. This positions non-conducting plunger 50 upwardly and directly against floating contact 42, raising both contact 42 and contact 40, and

holding these two contacts apart from contact sleeve 44 which, it will be remembered, is fixed in its position. Consequently, the switch means 18 is in an open condition, and there is no current flow through it.

When the engine is decelerated to produce the required vacuum, the above con-ditions are changed. The balanced forces upon the diaphragm are unbalanced by the decrease in manifold pressure (i.e., increase in vacuum), and as a result spring 38 and the atmospheric pressure within the cover are now able to force the diaphragm downward. If the vacuum is sufiiciently large, the diaphragm will travel downward until plunger 50 has been lowered enough to allow contact 42 to touch the contact sleeve 44. When this occurs, a path is completed for current flow through the contact sleeve, the adjacent ring plate 48, and the switch housing 20. Due to its direct mechanical engagement with the intake manifold and engine block, the switch housing is effectively at ground potential, and circuit branch 16 of FIG. 1 is completed to cause the indication noted.

Quite clearly, when the engine is subsequently either accelerated or merely brought to a steady state of operation at a new power setting, the vacuum in the intake manifold will again resume its previous level. This will cause the diaphragm to shift upwardly once again to open the contacts and extinguish the alarm signal. Furthermore, the point at which the switch means 18 opens and closes its contacts may be varied by adjustment of screw 34, which either decreases or increases the amount of compressive force which spring 38 exerts against the diaphragm. The greater this force is, the sooner the contacts will close. That is, the switch will close at reduced levels of vacuum in the manifold representing lesser degrees of deceleration. By this adjustment, the optimum condition may be produced with any engine, where the signal is extinguished under normal idle conditions but is actuated under a minimum degree of deceleration.

It should be pointed out that by the use of the present invention two very important results are obtained. In the first place, typical signal lamps have practically no coldfiiament resistance. Consequently, when they are initially energized they draw very large currents in the form of a surge which decreases quickly with time as the filaments rapidly heat to operating temperatures. Thus, where, as in the present case, a bulb requires an operating current of perhaps 1.5 amperes, that bulb will draw as much as twenty amperes when first energized. This tremendous surge of current is exceedingly detrimental to both the bulbs and the switching contacts, particularly the contacts in switching means of the general nature of the vacuum-sensing switch of the present invention. Indeed, even with expensive metals such as tungsten forming the contacts, such switches will not endure large surges over the extended usage required in the present installation. Instead, they rapidly pit and become fouled to render the device useless.

In the present invention, the small current present at all times in the filaments of the bulb keeps them in a heated condition and prevents large surges of energizing current when the bulb is suddenly switched on the switch 18. Consequently, the contacts used in the switch means are not placed under extreme operating conditions and conduct only currents which are more or less the same as the steady-state operating current. Under these conditions the contacts last practically indefinitely. Moreover, they need not be formed from expensive metals, but common contact material such as Phosphor bronze may be used and will provide a switch having an exceedingly long operating life.

Also, previous vacuum-actuated switches similar to switch means 18 of the present invention embodied no means for making the contacts self-cleaning. Accordingly, their contacts were fouled at an unimpeded pace which contributed to unusably short operating lives. The novel floating contact washer 4'2. of the present invention has provided an effective and desirable solution to this problem. When the switch is open and the contacts not touching each other, and also when contact is broken by the plunger 56) lifting the floating contact 42 away from contact sleeve 44, the floating contact is free to move in random increments between contact Washer 49 and contact sleeve 44. Consequently, the normal vibrations of the motor vehicle, together with other similar influences cause the three different contact pieces to occupy relatively different positions practically each time they touch to close the switch. This provides a desirable wiping action serving to keep the contacts clean, and also greatly reducing burning and pitting by constantly changing the current-carrying contact areas.

In accordance with the foregoing, it will be clear that the present invention provides a novel deceleration alarm signal that successfully provides every characteristic demanded by the underlying problem which brought about its conception. It is completely reliable, has an extremely long operating life, its operation is completely automatic and is also substantially instantaneous. Moreover, the readily accessible adjustment feature ensures that the alarm may quickly be readjusted to operate successfully upon any and all of the many different varieties of internal combustion motor vehicles. Further, as the condition of a particular engine changes during extended use and aging, the alarm system of the present invention may simply be readjusted as the need requires, and it therefore will always operate properly, regardless of engine condition. Furthermore, and of the greatest importance, the present system is economical to manufacture and thus can be produced by present production techniques at a cost which does not detract from its desirability and which makes it available to persons of all income groups, not as a luxury but as an important safety device.

It may well be that following a thorough consideration of the foregoing description of the embodiment of this invention most preferred by me, those skilled in the art to which it pertains may conceive of various modifications and alterations in details which upon the spirit of this invention for their inspiration. All such modifications and variations are to be considered a part of the invention, unless the claims appended below by their language expressly state otherwise.

What is claimed is:

1. A vacuum-sensing switch means for use in a vehicle deceleration signal system, comprising: diaphragm means coupled to the intake manifold of said vehicle for sensing the level of vacuum therein; an electrical contact operatively coupled to said diaphragm to be moved by same; a fixed electrical contact; and a floating contact interposed between the other two said contacts and movable therebetween; said diaphragm contact moving relative to said floating contact and causing the latter to move relative to the fixed contact to make and break a circuit therethrough in response to said diaphragm sensing predetermined levels of vacuum in said manifold representative of the presence and absence of engine deceleration and moving corresponding predetermined distances in response thereto.

2. The switch means of claim 1, including means for adjusting the required contact-making movement of said diaphragm contact relative to said floating and fixed connonetheless dependtacts to correspond to various predetermined levels of said vacuum, whereby the making and breaking of said circuit through the three said contacts may be adjusted accordingly.

3. In an alarm system for signalling the deceleration of motor vehicles having internal combustion engines, of the type having an indicating device connected to an appropriate source of power and a vacuum-operated switch means operatively coupled with the intake manifold of said engine for sensing the amount of vacuum present therein, said switch means having a pair of electrical contacts interposed in circuit with said indicating device and said power source to complete a circuit through the former and actuate same in response to said switch means sensing a predetermined amount of vacuum in said manifold, the improvement comprising: a conductive element movably interposed between said switch means contacts; said element completing a circuit between said contacts when contacted thereby, but being movable with respect to said contacts when not contacted by both thereof, to shift positions therebetween and thereby keep said contacts clean and reduce pitting thereof caused by repeated electrical conduction between identical contact areas.

4. The improvement in alarm systems recited in claim 3, wherein said conductive element comprises a floating, freely movable member positioned between said switch means contacts to randomly shift positions therebetween.

5. The improvement in alarm systems recited in claim 3, wherein said indicating device comprises an incandescent lamp, and wherein impedance means is interposed in circuit with said lamp to complete a path for current flow therethrough independent of said switch means, said impedance means limiting current flow through said path to a value less than that required to drive said lamp into incandescence, to thereby merely maintain said lamp in a ready state, said switch means contacts connected with respect to said lamp and said impedance means such that actuation of said switch means increases current flow through said lamp to energize the same into incandescence, to thereby produce a visible signal indicative of deceleration of said vehicle.

6. The improve-ment in alarm systems recited in claim 5, wherein said impedance means comprises a resistor connected in series with said lamp, said switch means contacts being normally open and connected in shunt across said resistor to short the latter upon contact closure and thereby increase the current flow through said lamp to its point of incandescence.

7. The improvement in alarm systems recited in claim 6, wherein said conductive element comprises a floating, freely movable member positioned between said switch means contacts to randomly shift positions therebetween.

References Cited JOHN W. CALDWELL, Primary Examiner.

NEIL C. READ, THOMAS B. HABECKER,

Examiners.

A. H. WARING, Assistant Examiner, 

